#include <iostream>
#include <fstream>
#include <cstdlib>

using namespace std;

void file_it(ostream & os, double fo, const double fe[], int n);
const int LIMIT = 5;

int main(void)
{
	ofstream fout;
	const char * fn = "ep-data.txt";
	fout.open(fn);
	if( !fout.is_open() )
	{
		cout << "Can't open " << fn << ". BYE.\n";
		exit(EXIT_FAILURE);
	}
	double objective;
	cout << "enter the focal length of your telescope objective in mm: ";
	cin >> objective;
	double eps[LIMIT];
	cout << "enter the focal lengths, in mm, of "<< LIMIT <<"eyepieces:\n";
	for(int i=0;i< LIMIT;i++){
		cout << "eyepieces # " << i + 1 << ": ";
		cin >> eps[i];
	}
	file_it(fout, objective, eps, LIMIT);
	file_it(cout, objective, eps, LIMIT);
	cout << "Done.\n";
	
	return 0;
}

void file_it(ostream & os, double fo, const double fe[], int n)
{
	ios_base::fmtflags initial;
	initial = os.setf(ios_base::fixed);
	os.precision(0);
	os << "focal length of objective: " << fo << " mm\n";
	os.setf(ios::showpoint);
	os.precision(1);
	os.width(12);
	os << "f.l. eyepice ";
	os.width(15);
	os << "magnification" << endl;
	for(int i = 0; i < n; i++)
	{
		os.width(12);
		os << fe[i];
		os.width(15);
		os << int (fo/fe[i] + 0.5) << endl;
	} 
	os.setf(initial);
}

